1. Field of the Invention
The present invention relates to a water base ink for ink-jet recording to be used for an ink-jet recording apparatus provided with an ink-jet head having a metal member which is composed of nickel or an alloy containing nickel and which is disposed at least in an ink supply passage for supplying the ink to a discharge section.
2. Description of the Related Art
The printer technique based on the ink-jet recording system is a printing technique based on, for example, the bubble system in which the ink is discharged from minute nozzles by using bubbles generated by the rapid heating, or the piezoelectric system in which the ink is discharged from minute nozzles by using a piezoelectric element that is deformable when a voltage is applied. In this technique, the inks for ink-jet recording of several colors, which serve as the basic colors, are converted into minute liquid droplets of several picoliters to several tens picoliters, and they are selectively landed on the paper surface to form an image thereby.
The ink-jet recording system is advantageous in that the high printing or typing quality and the high print or photographic quality are successfully obtained by controlling the discharge of the minute liquid droplets. Colors approximate to those obtained by the full color system can be reproduced and images without involving any granular texture can be formed by allowing the minute ink droplets of several picoliters to land highly accurately on the paper surface from the discharge nozzles having minute diameters. It is important not to cause any clog-up in order to stably discharge the minute ink droplets from the discharge nozzles having the minute diameters. It is necessary to use the ink for ink-jet recording from which any dust and impurities are removed from the ink by the precise filtration or microfiltration after the preparation.
However, when the water base ink for ink-jet recording is used for a long period of time in an ink-jet head having a metal member which is composed of nickel or an alloy containing nickel and which is disposed in the ink supply passage, then the metal member is corroded and/or the metal ion of nickel or the like is eluted from the metal member due to the long term contact with the water base ink for ink-jet recording. Therefore, any metal oxide is produced in some cases. In other cases, when the coloring agent is a dye, the metal ion and the dye form an insoluble inorganic salt to produce any deposit, or when the coloring agent is a water-insoluble pigment, the pigment particles are coagulated and/or deposited due to the metal ion even when the particle diameters of the pigment particles are controlled upon the preparation of the ink. As a result, the following problems have arisen. That is, any clog-up occurs at the filter and the nozzle, and it is impossible to perform the discharge operation stably and highly accurately for a long period of time.
In view of the above, Japanese Patent Application Laid-open No. 2001-287455 discloses a technique in which benzoic acid is added as a rustproofing or rust preventing agent to an ink for ink-jet recording, and Japanese Patent Publication No. 7-122044 discloses a technique in which sodium benzoate is added as an antiseptic/fungicidal agent to an ink for ink-jet recording. However, there is no disclosure about whether or not the inks for ink-jet recording described above are usable for the ink-jet head based on the use of nickel or the alloy containing nickel. On the other hand, Japanese Patent Application Laid-open No. 11-116865 discloses a technique in which an azine-based coloring agent and a phosphorus compound for preventing metal corrosion are contained in a hot melt type ink in order to avoid any corrosion at portions which make contact with the ink and which are based on the use of, for example, nickel or phosphorylation-treated nickel.